Problem's that pesky freedom of speech thing, mostly, space. There's a lot of precedent mostly saying you can't interfere with folks attempts at politickin'. You can limit how they go about it, to a degree, but the SC is probably going to kick you in the ass if you try to stop it entirely. And a lifetime ban? Stuff like that's not going to fly. You might be able to get away with it if it was a
business doing something like that, in relation to their own business, but we'd be explicitly talking the government violating people's right to influence those government decisions via talkin', i.e. lobbying. Fund restrictions and whatnot are one thing, complete denial is a whole 'nother ballgame. There's not exactly a maximum time limit on the amount someone can try to influence decision making. Maybe you think that's unfortunate, but it's what we got.
Like, ferex.
Once a new guy is elected and power is peaceably transferred to new officials, why should the old officiajls be able to continue to influence government decisions?
The why is because I can influence those decisions. And you can. And
anyone in this country, by and large. There's no rationing system in place for freedom of speech. You can keep someone from holding office but you're going to have a hell of a time keeping them from talkin' to the folks that do. Legally, anyway.